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  <title>Document</title>
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  <script>
    var score = +prompt('请输入成绩');
    if (score >= 90) {
      alert('优秀');
    } else if (score >= 80) {
      alert('良好');
    } else if (score >= 60) {
      alert('及格');
    } else {
      alert('不及格');
    }
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